Apparatus for use in arcing fault detection systems

ABSTRACT

An apparatus for use in arcing fault detection systems within circuit breakers and which is adapted for automated production by top-down assembly. In one embodiment, the apparatus includes a circuit board and a two-piece sensing coil within a two piece housing with its center oriented horizontally relative to the circuit board. In other embodiments the sensing coil is one-piece and is either preassembled with a sensing bus and oriented horizontally or oriented vertically relative to the circuit board. Also included are several methods for making electrical connections to the circuit breakers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/600,512 filed Feb. 13, 1996, now U.S. Pat. No. 5,682,101 for“Arcing Fault Detection System”. U.S. patent application Ser. No.08/600,512 is a continuation in part of U.S. patent application Ser. No.08/402,678, filed Mar. 13, 1995 now abandoned and entitled “Device andMethod for Blocking Selected Arcing Fault Signals”; Ser. No. 08/402,600,filed Mar. 13, 1995 now abandoned and entitled “Voltage Sensing ArcingFault Detector and Method”; Ser. No. 08/402,575, filed Mar. 13, 1995 nowabandoned and entitled “Arcing, Fault Detection System and Method”; Ser.No. 08/403,084, filed Mar. 13, 1995 now abandoned and entitled “Deviceand Method for Testing Arcing Fault Detectors”; and Ser. No. 08/403,033,filed Mar. 13, 1995 now abandoned and entitled “Current Sensing ArcingFault Detector and Method”.

Each of the above applications has the same assignee as the presentinvention, and each is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to electrical circuit breakers and, moreparticularly, to apparatus and methods for assembling by automatedproduction miniature circuit breakers which contain arcing faultdetection systems.

BACKGROUND OF THE INVENTION

Electrical systems in residential, commercial and industrialapplications usually include a panelboard for receiving electrical powerfrom a utility source. The electrical power is then delivered from thepanelboard to designated branch circuits supplying one or more loads.Typically, various types of protective devices are connected to thebranch circuits to reduce the risk of injury, damage or fires, Theprotective devices may be mounted within the panelboard or external tothe panelboard.

Circuit breakers are a well known type of protective device which aredesigned to trip open and interrupt an electric circuit in response todetecting overloads and short circuits. Overload protection is providedby a thermal element which, when heated by the increased current, willcause the circuit breaker to trip and interrupt the power. This canoccur when too many loads draw power from the same branch circuit at thesame time, or when a single load draws more power than the branchcircuit is designed to carry. Short circuit protection is provided by anelectromagnetic element that trips when sensing high current flow.Additionally, many circuit breakers include ground fault interruption(GFI) circuitry to protect against ground faults which occur whencurrent flows from a hot conductor to ground through a person or object.

Arcing fault detectors are another type of protective device which maybe employed in an electrical distribution system. Arcing fault detectorsare designed to trip open and interrupt an electric circuit in responseto arcing faults, which occur when electric current “arcs” or flowsthrough ionized gas between two ends of a broken conductor, between twoconductors supplying a load, or between a conductor and ground. Arcingfaults typically result from corroded, worn or aged wiring orinsulation, loose connections, wiring damaged by nails or staplesthrough the insulation, and electrical stress caused by repeatedoverloading, lightning strikes, etc. The presence of an arcing faultcreates a significant fire hazard because it generates heat which mayignite the conductor insulation and adjacent combustible materials.Standard circuit breakers typically can not detect arcing faults becausebranch or load impedance may cause the level of load current to bereduced below the trip curve setting of a standard circuit breaker.

Each branch circuit of the electrical distribution system may include aselected combination of standard circuit breaker components, arcingfault detection circuitry or GFI circuitry to protect the branch circuitfrom associated hazardous conditions including overcurrents, arcingfaults and ground faults. Whatever combination is selected, it ispreferred that the protective devices are packaged together within aminiature circuit breaker housing adapted to be positioned within anelectrical distribution panelboard or load center.

The present invention relates to the production of circuit breakersincluding arcing fault detection components in conjunction with standardcircuit breaker components and/or GFI. Production of such circuitbreakers by automated equipment is desirable. Consequently, the presentinventors have sought improved arcing fault detectors which facilitateautomated production, or, if desired, manual assembly, through“top-down” methods, which require access from only one side of thecircuit breaker.

SUMMARY OF THE INVENTION

The present invention facilitates automated production (or handassembly) of circuit breakers which include arcing fault detectors. Suchdetectors comprise a toroidal sensor having an annular core encompassinga current-carrying load line in which the sensing coil is woundhelically on the core such as has been described in the patentapplications referenced above.

In one embodiment, the assembly includes a circuit board and a two-piecesensor core in a two piece housing. The lower sections of the core andhousing are connected to the circuit board and the upper sections of thecore and housing are detachably mountable to their respective lowersections. A helical winding is placed on the lower core and is attachedto conductive pins which make electrical contact with the circuit board.When the upper core is locked to the lower core, they form a hollowcenter oriented horizontally. Electrical power is supplied to anelectrical load via attachment to a load line terminal located on oneside of the sensing coil. The load line terminal extends through thehollow center of the sensing coil. An insulator is disposed around theportion of the load line terminal within the center of the sensing coil.A connection to the electrical supply is provided via a load terminalwhich is connected to the load line terminal after it has emerged on theopposite side of the sensing coil. In an alternative embodiment, theupper section of the housing is omitted.

In another embodiment, the sensing coil is positioned on the circuitboard so that the hollow center of the coil is oriented vertically andthe load line terminal is connected to the load terminal above thesensing coil. Alternatively, the sensing coil may be one-piece andpositioned with the hollow center mounted horizontally. In such anembodiment, the terminal would be inserted within the sensing coil andweld connections made to the load terminal and the circuit board afterthe sensing coil has been positioned.

In other embodiments the neutral terminal connection to the circuitbreaker is made through a strain relief member to facilitate automatedassembly.

The invention also includes a power connector to a circuit boardcomprising a clip for frictional engagement with the load line terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which comprise a portion of this disclosure:

FIG. 1a is a perspective view of a miniature circuit breaker housingadapted to be mounted to a panelboard and which may include componentsaccording to the present invention;

FIG. 1b is a plan view of a circuit breaker incorporating an arcingfault sensor packaged within the miniature circuit breaker housing ofFIG. 1a;

FIG. 2 is a perspective view of a sensing coil connected to an internalload connector and a load line terminal;

FIG. 3 is a partial perspective view of an alternate embodiment of thepower connection to the circuit board;

FIG. 4 is a partial perspective view of an alternative embodiment of thelower housing;

FIG. 5 is a perspective view of the housing and sensing coil;

FIG. 6 is a partial perspective view of an alternative connectionbetween the internal load connector and load line terminal;

FIG. 7 is a perspective view of an alternative embodiment of the sensingcoil and the connection of the internal load connector and the load lineterminal;

FIG. 8 is a partial perspective view of another alternative embodimentof the sensing coil of FIG. 7;

FIG. 9 is a perspective view of a lug connection;

FIG. 10 is a perspective view of a strain relief member;

FIG. 11 is a perspective view of an alternative strain relief member;

FIG. 12 is an elevation view and a perspective view of anotheralternative strain relief member;

FIG. 13 is an elevation view of a load line terminal of the presentinvention;

FIG. 14 is perspective view of another alternative embodiment employinga one-piece sensing coil horizontally mounted,

FIG. 15 is a perspective view of an alternative embodiment of thevertically positioned sensing coil of FIG. 7; and

FIG. 16 is a perspective view of another alternative embodiment of thevertically positioned sensing coil of FIG. 7.

DETAILED DESCRIPTION

This invention provides an improved apparatus and method for assemblingminiature circuit breakers incorporating arcing fault detection. Thisinvention is particularly useful for the automated assembly of miniaturecircuit breakers. The invention described herein, and all the preferredand alternative embodiments, allow for the efficient assembly of aminiature circuit breaker by manual or automated assembly to allow forincreased productivity, product quality and profitability. One method ofassembly that increases efficiency is “top down” assembly. Thisinvention facilitates top down assembly by its use of components such asthe two piece core and housing, the power connector clip, the slottedconnectors, and the slotted circuit board configured to receive theclamp terminal with flanges. This invention also eliminates the need forflexible discrete wiring. Moreover, by employing pinch weld technologyand top down assembly, this invention makes the efficient and economicalmass production of miniature circuit breakers a reality Of course, handassembly is facilitated also, if it is used rather than automatedproduction.

The invention relates to miniature circuit breakers which include arcingfault and/or ground fault detection systems operating in conjunctionwith standard circuit breaker components Generally, the miniaturecircuit breaker will be enclosed in an insulating case and adapted toclip into an electrical panelboard, through which electrical power isdistributed from a utility source to a plurality of branch circuits eachdefined by line and neutral conductors supplying electrical power to aload. The circuit breaker is electrically connected to both the line andneutral conductors and is designed to interrupt current in an associatedbranch circuit upon the occurrence of an arcing fault and/or groundfault, overcurrent or short circuit condition.

FIG. 1a provides a perspective view of a miniature circuit breakerhousing generally designated by reference numeral 61. The miniaturecircuit breaker housing 61 is comprised of an electrically-insulatingbase 63 closed at one face by a detachable cover 65 which togetherenclose the components of a miniature circuit breaker, which maycomprise a standard circuit breaker, a ground fault interrupter module,an arcing fault detection system or any combination thereof. TheQuik-Gard® circuit breaker, sold commercially by Square D Company, CedarRapids, Iowa represents an example of a product including standardcircuit breaker components and a ground fault interrupter within aminiature circuit breaker housing. A clip 77 is provided for mountingthe housing 61 to a mounting bracket 87 of a panelboard 75 of anelectrical distribution system. A electrically-conductive jaw-liketerminal 69 a or bolt terminal 69 b extends through the base 63 to beexternally connected to a line bus bar 73 within the panelboard 75.Similarly, a panel neutral conductor 79 extends through the housing 61for connection to a neutral bar 81 in the panelboard 75. Externalconnections to the line and neutral conductors leading to the load of abranch circuit of the electrical distribution system are providedthrough a load line conductor 83 and load neutral conductor 85,respectively.

FIG. 1b illustrates a plan view of a circuit breaker 1 includingstandard circuit breaker components and arcing fault detectioncomponents disposed within the miniature circuit breaker housing 61shown in FIG. 1a. As depicted in FIG. 1b, the miniature circuit breaker1 is in a closed position, enabling line current to flow completelythrough the circuit breaker and toward the load of a designated branchcircuit. Line current enters the circuit breaker 1 through the jaw-liketerminal 69 a and flows through a stationary contact carrier 89 integralwith the jaw like terminal 69 a. The stationary contact carrier 89 has astationary contact 2 mounted thereon. A movable contact 3 mounted to amovable contact carrier 91 abuts against the stationary contact 2 whenthe circuit breaker 1 is in the closed position. Line current therebyflows from the stationary contact carrier 89 to the movable contactcarrier 91 through the stationary and movable contacts 2 and 3,respectively.

A pigtail conductor 93 is electrically connected at one end to themovable contact carrier 91 and at another end to a yoke 95, enablingline current to flow from the movable contact carrier 91 to the yoke 95when contacts 2 and 3 are in a closed position. A bimetal conductor 97composed of two dissimilar thermostat materials is electricallyconnected to the yoke 95. The bimetal conductor 97 is electricallyconnected to an internal line conductor 101 which is connected to a loadterminal 105. When contacts 2 and 3 are in the closed position, linecurrent flows from the yoke 95 through the bimetal conductor 97 andthrough the internal line conductor 101. Thereafter, current flowingthrough the internal line conductor 101 passes through a sensing coil103 which monitors the rate of change of line current flowing throughthe circuit breaker 1. The present invention in one aspect is related tomethods for assembling certain components associated with sensing coil103.

After exiting the sensing coil 103, the line current flows to a loadterminal 105 to which the load line conductor 83 (FIG. 1a) may beattached to provide the line current to a load. The line current iselectrically connected to circuit board 123 at connection 105 a. Thepresent invention in one aspect is related to methods and apparatus forconnecting the load line conductor 83 to the load line terminal 105. Theminiature circuit breaker 1 also includes a load neutral terminal 107 towhich the load neutral conductor 85 (FIG. 1a) may be attached. Theminiature circuit breaker further includes an internal neutral conductoris electrically connected to the neutral terminal 107 and the panelneutral conductor 79 described in relation to FIG. 1a. The internalneutral conductor is electrically connected to the circuit board 123 atconnection 79 a. The present invention in one aspect is related tomethods and apparatus for connecting the internal neutral conductor,panel neutral conductor and load neutral conductor to the load neutralterminal 107. In embodiments with ground fault interruption (GFI)circuitry (not shown), the load neutral conductor would be routedthrough the sensor 103 along with the internal line conductor 101 topermit sensing of an imbalance of current flow between the internal lineand neutral conductors 101 and 79 as is known in the art. A morecomplete description of GFI circuitry is disclosed in U.S. Pat. No.5,446,431, assigned to the instant assignee and incorporated herein byreference.

The circuit breaker i may be tripped open in any of several ways,including manual control and in response to thermally andelectromagnetically-sensed overload conditions and ground faultconditions. The mechanism for tripping open the circuit breaker 1 isdescribed in detail in U.S. Pat. No. 5,446,431, assigned to the assigneeof the present invention and incorporated herein by reference.Accordingly, it will be described only briefly herein.

The miniature circuit breaker 1 may be moved between the open and closedpositions by a user manually moving the operating handle 111 to theright or left, respectively, causing corresponding movement of the topof the movable contact carrier 91 to the left or right of a pivot point.A toggle spring 113 is connected at one end to the operating handle 111and at another end to the movable contact carrier 91. When the top ofthe movable contact carrier 91 is left of the handle pivot point, thetoggle spring 113 serves to bias the bottom of the movable contactcarrier 91 to the open position. Conversely, when the top of the movablecontact carrier 91 is right of the pivot point, the toggle spring 113biases the bottom of the movable contact carrier 91 to the closedposition.

The miniature circuit breaker 1 is also designed to be tripped open inresponse to sensing various types of fault conditions. Upon theoccurrence of a moderately sustained overload condition when thecontacts 2 and 3 are in a closed position, the bimetal conductor 97becomes heated and the lower end bends to the right The bimetalconductor 97 may be adjusted by calibration screw 133. Bending of thebimetal conductor 97 by differential expansion causes an armature 115and yoke 95 to swing counterclockwise and release a trip lever 117. Thetrip lever 117 rotates clockwise about pin 1199 causing the togglespring 113 to pull the bottom of the movable contact carrier 91 awayfrom the stationary contact 2 and interrupt the current path.

Similarly, upon the occurrence of an extensive current overloadcondition, a high magnetic flux field is created around the yoke 95. Thearmature 115 is drawn toward the yoke 95 by the magnetic field, causingthe trip lever 117 to become released from the armature 115. Asdescribed in relation to thermal trips, release of the trip lever 117from the armature 115 causes the toggle spring 113 to pull the bottom ofthe movable contact carrier 91 away from the stationary contact 2 andinterrupt the current path.

Finally, electronic components 121 mounted on a circuit board 123 areprovided for processing the signal output of the sensor 103 anddetermining whether an arcing fault condition or ground fault conditionare present. The electronic components 121 are preferably the same asthose described in pending U.S. patent application Ser. No. 08/600,512,but it will be appreciated that any configuration of electroniccomponents 92 known in the art for detecting arcing faults may beprovided. Similarly, the electronic components 121 may reflect anyconfiguration known in the art for sensing ground faults. At any rate,the electronic components 121 are designed to produce an “AFD” and/or“GFI” trip signal corresponding to whether the circuit breaker 1 isdesigned to sense arcing faults and/or ground faults. In response togeneration of either an AFD or a GFI trip signal, a magnetic field iscreated around a trip solenoid 125, causing a plunger 127 to be drawn tothe right. The plunger 127 is connected to a trip link 129, which inturn is connected to the armature 115, such that movement of the plunger127 causes the armature 115 to be drawn to the right. As previouslydescribed, movement of the armature 115 to the right causes the triplever 117 to be released and the current path through the circuitbreaker 1 to be interrupted.

In an alternative embodiment of the present inventions the electroniccomponents 121 may also be designed to generate a thermal/magnetic tripsignal in response to overloads or short circuits, thus obviating theneed for the bimetal, yoke and armature associated with the prior art.This capability is described in detail in U.S. Pat. No. 5,136,457,assigned to the assignee of the present invention and incorporatedherein by reference. In this embodiment, the thermal/magnetic tripsignal will cause the contacts of the circuit breaker 1 to be opened insubstantially the same manner as they would in response to an AFD or aGFI trip signal.

FIGS. 2 and 5 show an assembly 10 which includes a printed circuit board12 (FIG. 2 only) and a housing 14. The housing 14 has a removable uppersection 16 and a lower section 18 which is connected to the circuitboard 12. The sensing coil 20 comprises an upper core section 22 and alower core section 24 (see FIG. 5). A winding 26 surrounds the lowercore section 22, as best illustrated in FIG. 5. Each end of winding 26is connected to a respective one of the electrically conductive pins 27which continue through the housing 14 and thus are electrically attachedto the circuit board 12. The upper core section 22 interlocks with thelower core section 24 to form a horizontally oriented hollow center 60through which the line conductor (or both line and neutral conductors)of the circuit breaker are designed to pass. The upper section 16 of thehousing 14 has a pair of catches 19 for snapping onto a respective pairof ramps 17 on the lower section 18. Thus, the upper and lower sectionssubstantially enclose the sensing coil 20. It is feasible to omit uppersection 16 if desired, in which case the outer cover (65 in FIG. 1a)serves as the upper housing. The housing 14 has a pair of openings 15through which load line terminal 28 extends. These openings may havedifferent configurations (e.g compare FIGS. 2 and 5 depending on theshape of the load line terminal.

Returning to FIG. 2, load line terminal 28 has a long end 30 and a shortend 32. The long end 30 is partially surrounded with insulator 34 whereit passes through the hollow center of sensing coil 20. The long end 30is disposed in sensing coil 20 so that the insulator 34 extends beyondthe sensing coil 20 and through the opening 15. Line current passesthrough load terminal 36 which is connected to the long end 30 of loadline terminal 28. Preferably, load terminal 36 is connected to long end30 by a pinch weld as shown. Calibration screw 38 is disposed in loadterminal 36 so that a portion of calibration screw 38 extends past loadterminal 36.

Power is supplied to circuit board 12 via a connection to the load lineterminal 28. In one embodiment, the connection is via clip 42 forfrictionally and electrically engaging the short end 32 of load lineterminal 28. Alternatively, the connection 42 can include a leaf spring44 that is pinch welded to the short end 32 of load line terminal 28, asshown in FIG. 3.

In a preferred embodiment illustrated in FIG. 4, lower section 18 ofhousing 14 can include an insulating channel 46 for insulating thecalibration screw 38 and a screw driver inserted into the circuitbreaker from the components on the circuit board 12. The insulatingchannel 46 is substantially U-shaped and configured to receive thecalibration screw 38 and to assist in the alignment of a screw driverwith the head of calibration screw 38. The insulating channel 46 isconnected to or is integral with the lower section 18 of housing 14.

FIG. 6 illustrates an alternative connection between the load terminal36 and load line terminal 28. In one embodiment, load terminal 36 has aslot 32 that is configured to receive the long end 30 of the load lineterminal 28. In an alternative embodiment (not shown), the load lineterminal 28 has a similar slot that is configured to receive the end ofload terminal 36.

FIG. 7 illustrates an alternative embodiment in which the hollow center60 of sensor 20 is oriented vertically rather than horizontally. Thus,the terminals pass vertically rather than horizontally through the coilas in the embodiment discussed above. Here, a sensor bus 54, which has afirst end portion 56 and a second end portion 58, is connected tocircuit board 12 through slots 55. The sensing coil 20 is disposedaround the first end portion 56. Load terminal 36 is connected to thefirst end portion 56. Load line terminal 28 is connected to the secondend portion 58. Preferably, both connections are made by pinch weldingas shown. FIG. 8 illustrates an alternative embodiment wherein the loadline terminal 28 and the sensor bus 54 are made from a single piece ofmetal.

FIGS. 14-16 illustrate additional constructions to those shown in FIGS.4 and 7-8 respectively. FIG. 14 shows a one-piece sensing coil 14A withthe hollow center oriented horizontally. The load line terminal 28A ispreassembled with the sensing coil 14A and placed on the circuit board,12A and then pinch welded to the load terminal 36A and the circuit boardconnector 42A. A screw terminal may be used to connect the power supplyas shown.

FIGS. 15 and 16 show a one-piece sensing coil (14B and 14C) with thehollow center oriented vertically. In those constructions, power issupplied through connections either under the circuit board (12B FIG.16) or above the circuit board (12C FIG. 15). The connections to theload terminal (36B and 36C) are made by pinch welding above the sensingcoil (14B and 14C), again facilitating top-down assembly.

Flexible, but restrained, wire terminations are important features ofthe circuit breakers of the invention to facilitate their automatedassembly. Alternative methods of providing such wire terminations areshown in FIGS. 9-12.

A lug connection 62 is illustrated in FIG. 9. The lug 62 includes a top64 and a hollow center 66. The top 64 includes a hole 68 connecting thetop 64 to the hollow center 66. A neutral bus 70 which is connected viawire 82 to the panel neutral (not shown) is connected by lug 62 to theload neutral via wire 78. End 72 of bus 70 is positioned inside of thehollow center 66 of the lug 62 and extends underneath the hole 68. Awire binding screw 76 is disposed in the hole 68 and extends through thehollow center 66 in order to secure wire 78 between end 72 of theneutral bus 70 and bottom 71 of hollow center 66. A strain relief member80 is provided at end 74 of the neutral bus 70.

Turning to FIG. 10, there is shown a strain relief member 80 whichincludes a top section 84 for connecting the load neutral wire (shown as78 in FIG. 9) and a bottom section 86. The top section 84 issubstantially flat and includes a hole 90 disposed therein. The loadneutral wire is clamped between the flat section and a second matingplate (not shown) by means of a screw (not shown) threaded into hole 90.Strain relief region 92 defines a cavity 94 for receiving the panelneutral wire. The bottom section 86 forms a cylinder 92 which defines acavity 94. The top section 84 and the bottom section 86 are connectedtogether and separated by a solid member 96. Connected to the topsection 84 of strain relief member 80 is a wire 98 (corresponding towire 82 of FIG. 9). The wire 98 extends through the cavity 94 formed bythe bottom section 86 and is secured therein in order to prevent strainon the connection of wire 98 to top section 84. In a preferredembodiment, the wire 98 is pinch welded to top section 84 as shown.

In an alternative embodiment illustrated in FIG. 11, wire 98 isconnected to the solid member 96 of the strain relief member 80. Thewire 98 extends through cavity 94 in order to prevent strain on theconnection of wire 98 to solid member 96. Preferably, the wire 98 ispinch welded to solid member 96. As described in FIG. 10 the loadneutral wire 78 (of FIG. 9) would be clamped to the upper section 84.

In another alternative embodiment illustrated in FIG. 12, the loadneutral wire is shown connected to the top section 84 by a screw 100 aspreviously described in connection with FIGS. 10-11. The panel neutralwire 98 is connected to the bottom section 86 of the strain reliefmember 80. Strain relief section 92 prevents strain on the connection ofwire 98.

FIG. 13 illustrates an embodiment in which a slot 106 is provided in theouter edge of the circuit board 12 to receive a clip which secures loadline terminal 28 (see FIG. 3) The bottom sections of the clip 108 andthe clamp terminal 28 are disposed in the slot 106 of the circuit board12. Extending from the bottom of the clip and the clamp terminal areflanges 110 which are configured to limit the load line terminal 28 frommoving in any direction except towards the center the circuit board 12.

While particular embodiments and applications of the present inventionhave been illustrated and described, it is to be understood that theinvention is not limited to the precise construction and compositionsdisclosed herein and that various modifications, changes, and variationswill be apparent from the foregoing descriptions without departing fromthe spirit and scope of the invention as defined in the appended claims.

What is claimed is:
 1. An apparatus for use in arcing fault detectionsystems, said apparatus comprising: a plurality of components adaptedfor top-down assembly, said components comprising: a circuit board; asensing coil housing having at least a lower section connected to thecircuit board; a sensing coil having a hollow center passageway orientedhorizontally relative to said circuit board; a load line terminal forconnection to an electrical load on one side of said sensing coil andextending through the hollow center of the sensing coil and the housing,the portion of said load line terminal within said housing and saidsensing coil being surrounded by an insulator; a load terminal connectedto the load line terminal on the side of the sensing coil opposite theelectrical load connection; said sensing coil comprising a generallyannular core including a lower core mounted in the lower housing sectionand an upper core detachably mounted to said lower core, and a windingonly on said lower core, said winding on said lower core being connectedto conductive pins in electrical contact with said circuit board, andsaid upper core being attachable and interlockable to said lower corefollowing introduction of said load line terminal into the lower core; acalibration screw extending through the load terminal; and wherein thelower section of housing includes an insulating channel for insulatingthe calibration screw, the insulating channel being substantiallyU-shaped and configured to receive the calibration screw therebyassisting the alignment of a screw driver with the calibration screw,the insulating channel being connected to the lower section of thehousing.
 2. The apparatus of claim 1, further comprising a powerconnector between said load line terminal and said circuit board.
 3. Theapparatus of claim 2 wherein said power connector is pinch welded to theload line terminal.
 4. The apparatus of claim 2 wherein said powerconnector is frictionally engaged to the load line terminal.
 5. Theapparatus of claim 1, wherein the load line terminal and load terminalare each made from the same single piece of metal.
 6. The apparatus ofclaim 1, wherein the load line terminal and the load terminal are joinedby a pinch weld.
 7. The apparatus of claim 1, wherein the load lineterminal and the load terminal are joined by a slot in one of saidterminals configured to receive an end of the other of said terminals.8. The apparatus of claim 1, said housing further comprising an uppersection detachably mountable to the lower section.
 9. An apparatus foruse in arcing fault detection systems, said apparatus being adapted forautomated production and comprising: a circuit board, a sensing coilhousing having at least a lower section connected to the circuit board;a sensing coil having a hollow center passageway oriented horizontallyrelative to said circuit board; a load line terminal for connection toan electrical load on one side of said sensing coil and extendingthrough the hollow center of the sensing coil and the housing, theportion of said load line terminal within said housing and said sensingcoil being surrounded by an insulator; a load terminal connected to theload line terminal on the side of the sensing coil opposite theelectrical load connection; said sensing coil comprising a generallyannular core including a lower core mounted in the lower housing sectionand an upper core detachably mounted to said lower core, and a windingonly on said lower core, said winding on said lower core being connectedto conductive pins in electrical contact with said circuit board, andsaid upper core being attachable and interlockable to said lower corefollowing introduction of said load line terminal into the lower core; acalibration screw extending through the load terminal; and an insulatingchannel for insulating the calibration screw, the insulating channelbeing substantially U-shaped and configured and located to receive thecalibration screw thereby assisting the alignment of a screw driver withthe calibration screw, the insulating channel being connected to thelower section of the housing and also configured and located forprotecting the circuit board from tool damage, for allowing electroniccomponents to be placed on the circuit board without threat of physicalor electrical damage due to a screw driver adjustment of the calibrationscrew and for guiding a screw driver into engagement with thecalibration screw.